Last year I used the GS criteria as explained in the book to rate two campgrounds. Following the criteria in the rating sheets led to ratings within 1 point in each criteria. The scoring sheets are actually pretty objective. Try it next time you have a chance.
The book will tell you a public campground exists and what services are available, but it doesn't rate them.
There are many private and public campgrounds that are not listed in the book.
Like kknowlton we don't search out the highest rating. Our first criteria is a star on the restroom rating with a rating or 7 or 8. We also like the GS members since they have to meet a minimum rating to be listed.